1. Field of the Invention
The present invention relates to a composition for metal electroplating comprising a leveling agent.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Filling of small features, such as vias and trenches, by copper electroplating is an essential part of the semiconductor manufacture process. It is well known, that the presence of organic substances as additives in the electroplating bath can be crucial in achieving a uniform metal deposit on a substrate surface and in avoiding defects, such as voids and seams, within the copper lines.
One class of additives are the so-called levelers. Levelers are used to provide a substantially planar surface over the filled features. In literature, a variety of different leveling compounds has been described. In most cases, leveling compounds are N-containing and optionally substituted and/or quaternized polymers, such as polyethylene imine, polyglycine, poly(allylamine), polyaniline (sulfonated), polyurea, polyacrylamide, poly(melamine-co-formaldehyde) (US 2004/0187731), reaction products of amines with epichlorohydrin (U.S. Pat. No. 6,610,192), reaction products of an amine, epichlorohydrin, and polyalkylene oxide (EP 1 371 757 A1), reaction products of an amine with a polyepoxide (EP 1 619 274 A2), polyvinylpyridine, polyvinylimidazole (US 2003/0168343 A1), and polyvinylpyrrolidone (U.S. Pat. No. 6,024,857).
However, none of the documents cited discloses the use of polyalkanolamines, alkoxylated polyalkanolamines, functionalized polyalkanolamines, or functionalized alkoxylated polyalkanolamines as additives for copper electroplating baths.
Polyalkanolamines can be synthesized by condensation of alkanolamines in the presence of an acidic or basic catalyst or metal salt as described in U.S. Pat. No. 2,407,895, EP 0 441 198 or U.S. Pat. No. 5,393,463. A co-condensation of alkanolamines with other hydroxyl-containing molecules like pentaerythritol, sorbitol, glycol, glycerol has been described in EP 0 057 398. The functionalization, i.e. quaternization of nitrogen atoms, of polydialkanolamines is described in EP-A-0057398 and EP-A-0160872.
European patent application No. 07120393.9, which was yet to be published at the priority date of the present application, discloses alkoxylated polyalkanolamines. They are prepared by means of a two-stage process in which, in a first step, amino alcohols are condensed to give polyalkanolamines, and the resulting polyalkanolamines are optionally alkoxylated in a second step. Functionalized alkoxylated polyalkanolamines are disclosed in the same application as well.